Hi there, new to the hobby, have set up an 80 gallon saltwater tank with a fluval 405, + a rio 800 power head in the tank, have had 5 blue devil damsels for 10 days, doing well, water looks good. Have brown algea on bottom only. I've been told to leave it be, true? how long will it hang around ?

Hi there, new to the hobby, have set up an 80 gallon saltwater tank with a fluval 405, + a rio 800 power head in the tank, have had 5 blue devil damsels for 10 days, doing well, water looks good. Have brown algea on bottom only. I've been told to leave it be, true? how long will it hang around ?

amonia = .25
NO2 = 0
NO 3 = 10
Ph = 8.2
TEMP = 78

Your tank is cycling, and from the looks on the water params, it seems to be doing so quite hard. .25 ammonia is quite high. How much live rock is in the tank? What type of substrate do you have? (live sand or crushed coral?)

Were you also warned that in 80 gallons with 5 blue devil damsels, you won't have much option for other fish? The blue devil damsels are about the most aggressive fish in the damsel category, along with things like the geribaldi and domino damsels. A group of these fish will destroy most others, regardless of size.... limit that group to an 80 gallon tank, you could have quite a mess!

As for what to do right now, I would suggest about 10 gallon water change every other day until that ammonia level begins to break down, make sure you have as much live rock in the tank as is possible, and be patient. Blue devils are pretty sturdy, but watch feeding time... make sure they finish all food within 1 - 2 minutes. If they don't finish it, then you must remove the uneaten food to avoid it from breaking down and polluting the tank. If you find that food is falling to the bottom and not being eaten in that time frame, decrease the amount you are offering by 1/2.

I'll watch for your reply because knowing what is in your tank will help to determine how much "work" you'll be in for during cycling, and can maybe make some suggestions on how to help it along in a good way.

About 15lb's live rock and live sand
The blued damsels certianly do seem aggresive but were suggested as a cycling fish. The fish are to be returned to the store where i will recieve store credit towards other fish. They also are the ones who said don't vaccum or change any water for one month. I feed every two days- Spectrum Thera = A, two pellets per fish and they inhale it.

All sounds pretty good except the amount of live rock in the tank. An 80 gallon tank should have as close to 80 lbs of rock as you can fit into it. (or more).
When dealing with saltwater you depend a lot more on biological filtration. This is the bacteria that breaks down waste to a safer form... which is then typically removed with water changes. The bacteria need places to culture, so filter media, sand bed, and rock are extremely important because those are the 3 biggest places your bacteria culture will grow. Without enough bacteria, your tank will not find stability, will take much longer to cycle, and depending on population, may never build enough bacteria to become or remain stable.
Fish waste product is toxic, and while your blue devils may be sturdier than many other fish, they are not immune to the physical problems that toxic water conditions will cause. Ammonia and nitrite are both toxic in any amount, and when we cycle a saltwater tank, mostly its done using live rock and sand, to protect the fish. A typical cycling period for a saltwater tank is about 6 - 8 wks.
In your situation, there isn't much rock, so bacteria has less places to culture, plus there is added waste in the tank from the fish. Your ammonia levels are rising due to this waste level, but your bacteria culture has not yet populated to begin breaking it down. If your ammonia level goes too much higher, even something like the blue devils are going to struggle to stay alive.
My 2 suggestions for you would be small 10% water changes (about 8 gallons) every other day, and also add as much more rock to the tank as you can. The rock itself will bring in waste, as changing environments will usually cause what is called "die off". Die off is the waste produced when things living in and on the rock begin to die from rapid changes in environment. The water changes should help to relieve some of the ammonia, while the rock and sand and filter allow for places to populate your nitrifying bacteria growth.

If the tank is left alone completely, don't be surprised if you have problems with the fish soon, which can make this type of problem even worse.
If your tank had 75 - 80 lbs of rock in it, I would say watch it closely, and if ammonia goes any higher, still do those small water changes, but just be patient and let it be. You need rock... a lot of it!

Thankyou for the tips. I'm not sure what direction I'm going to go, while I like the idea of a reef at some point, I have alot to learn so for now while the tank and I get to know each other I'm reading "The contientious Marine Aquarist" and plying the local fish stores for ideas. Any suggestions would be appreciated greatly.